Annually, over 5.7 million Americans are diagnosed with intervertebral disc disorders. As shown in FIG. 1, an intervertebral disc 12 includes the nucleus pulposus 10 surrounded by the annulus fibrosus 16. A disc 12 forms a cushion between adjacent vertebrae 14 and supports compressive loads during activities of daily living. Intervertebral disc disorders include intervertebral herniation (a mechanical disruption of the annulus fibrosus) and degeneration (which initiates within the nucleus pulposus). These pathologies can lead to a loss in disc height, impaired mechanical function, and long-term pain and disability.
Current therapies for both intervertebral disc degeneration and herniation are palliative and often only delay invasive surgical management in the form of discectomy, spinal fusion or total disc replacement. While these procedures may temporarily relieve pain, they do not attempt to replace, restore or regenerate damaged tissue with healthy biological tissue. Moreover, surgical approaches can provide long term solution to particular problems, but there are concerns with the use of surgical methodologies that may promote re-herniation, altered spinal biomechanics, and accelerated degeneration in adjacent discs.
The annulus fibrosus is an oriented lamellar structure with unique properties that are not easily matched. The unique hierarchical structure provides the mechanical strength necessary for physiologically function. Mechanically, the annulus fibrosus is highly anisotropic, heterogeneous, and nonlinear and serves the dual mechanical roles of restraining nucleus pulposus intradiscal pressure and connecting adjacent vertebrae. Various suturing techniques, adhesives, and natural and synthetic biomaterials have been developed in an attempt to provide materials and methods for functional repair of annulus fibrosus herniation and/or degeneration. While some of these approaches have demonstrated an amount of success toward cell adhesion, proliferation, and extra cellular matrix (ECM) production, none have illustrated comparable structural and mechanical characteristics of the native annulus fibrosus concomitant with the ability to support tissue regeneration. For instance, simply suturing herniation in annulus fibrosus tissue does not adequately fill the voids left by the original tissue damage, bioadhesives have not proven strong enough to adequately withstand the mechanical environment of the annulus fibrosus, occlusive mesh implants have likewise not met the necessary mechanical strength standards, and materials that can provide high mechanical strength, such as certain electrospun materials, are not cost effective and present serious scalability issues. In particular, no biomaterial has been developed that can effectively mimic the angle-ply collagen architecture and mechanical properties of the native annulus fibrosus while supporting natural cell ingrowth and proliferation.
What is needed in the art is a biomimetic biomaterial that can be utilized in intervertebral disc herniation or degeneration repair, among other applications, that can provide both structural characteristics to provide high functionality and cellular compatibility to encourage development of healthy tissue in the implant area. Furthermore, it would be beneficial to devise a simple, scalable process by which to manufacture the biomimetic biomaterial.